Designing for IE6 means you must consider its lack of support for PNG transparency. There are many PNG hacks out there, I prefer this one from Unit Interactive Labs . The problem with this one is that it has to read through the whole page searching for PNGs to fix which cna make load times noticable slower. I was trying top find a faster solution when I remembered that SharePoint uses PNGs on some of its pages.
On the all items view of most lists Sharepoint uses a png image. Built into the core code is a png fix that allows this image to work in IE6. You can take advantage of the built in png fix by using the following tag:
<asp:Content ContentPlaceHolderId="YourPlaceHolderName" runat="server"> <SharePoint:ViewIcon Width="widthInPx" Height="heightInPx" runat="server"></asp:Content>
The tag will need to be inside of a content placeholder tag. You can name the placeholder whatever you want that makes sense. The placeholder canb be wrapped in a DIV tag for positioning purposes.
The ViewIcon tag will require a width and height to render properly and will not work for background images.